The 315W CMH Grow Light has a high efficiency electronic ballast with no acoustic resonance.  The 315w CMH ballast uses a high temperature, resin-sealed componenet board for completely silent operation with a fan.  Each unit is burned-in at the factory for approximately twelve hours to ensure maximum reliability.

The improved, broader spectrum is achieved with the Veg 4200K lamp.  This fixture is used Greenhouse and Warehouse applications.